SUBJECT: M.S. Thesis Presentation
BY: Samuel Kim
TIME: Monday, April 7, 2014, 3:00 p.m.
PLACE: Love Building, 109
TITLE: Addressing Thermal and Environmental Reliability in GaN-based High Electron Mobility Transistors
COMMITTEE: Dr. Samuel Graham, Chair (ME)
Dr. Baratunde A. Cola (ME)
Dr. Shyh-Chiang Shen (ECE)


AlGaN/GaN high electron mobility transistors (HEMTs) have appeared as attractive candidates for high power, high frequency, and high temperature operation at microwave frequencies. In particular, these devices are being considered for use in the area of high RF power for microwave and millimeter wave communications transmitter applications at frequencies greater than 100 GHz and at temperatures greater than about 150 C. However, there are concerns regarding the reliability of AlGaN/GaN HEMTs.

Thermal reliability is the chief concern since high channel temperatures significantly affect the lifetime of the devices. Therefore, it is necessary to find the solutions to decrease the temperature of AlGaN/GaN HEMTs. In this study, we explored the methods to reduce the channel temperature via high thermal conductivity diamond as substrates of GaN. Experimental verification of AlGaN/GaN HEMTs on diamond substrates was performed using micro-Raman spectroscopy, and investigation of the design space for devices was conducted using finite element analysis as well.

In addition to the thermal impact on reliability, environmental effects can also play a role in device degradation. Using high density and pinhole free films deposited using atomic layer deposition, we explore the effect of ultra-thin barrier films for the protection of AlGaN/GaN HEMTs in high humidity and high temperature environments.